The "R months" myth
The traditional rule says to eat oysters during "R months" (September to April). It predates the cold chain, when summer transport was risky. Today, oysters can be eaten safely year-round.
What actually changes is taste and texture across the oyster's cycle.
Milky oysters in summer
In summer, the breeding season, some oysters turn "milky": the flesh is creamier and lactic. It is not a flaw — many enthusiasts enjoy it. In winter, the oyster is firmer and more iodised.